Best way to create eBay Sniper?

I am trying to build an eBay sniper. I do see there's an PlaceOffer API which allows you to place bids.

I am a bit puzzled on how to go about implementing my automatic bidding. 1. eBay seems to not like snipers for affiliate reasons mostly. I understand I must opt out of the affiliate program. 2. Am I allowed to use the eBay API to place bids on other users' behaves? Or do I need to do it via UI automation with a tool such as Selenium where the tool logs in with the user's credentials and enters a bid and clicks the bid button?

Are you experienced in this area? Do you know what the best approach is?